The long range objective of this project is the description of the component molecular events involved in the replication of the negative strand viruses (myxo, paramyxo and rhabdo viruses). The topics that are currently being investigated are: 1. The origin of DI particles. 2. The mechanism of mRNA synthesis in VSV infected cells. 3. Viral infection of dissociated neuron cultures and its modulation by DI particles and antibody. 4. Synthesis and characterization of measles specific nucleic acid probe.